Method of making a commutator

ABSTRACT

A pair of annular blanks, one consisting of copper and one consisting of another metal, are confined in a die. A stamp is introduced into the die and the material of the blanks is coldextruded through an annular gap defined between the stamp and the die, to form a commutator ring an inner annular zone of which consists of the other metal, whereas an outer annular zone consists at least at one axial endface of copper. The other metal may be aluminum and will be cold-welded or fused with the copper at the interface of the two metals.

United States Patent Wilke et al. [4 May 23, 1972 [54] METHOD OF MAKING A 2,963,774 12/1960 Pike ..29/597 CQMIVIUTATOR 3,005,920 10/1961 Dolza .29/597 X 3,177,562 4/1965 Werner et a1 ..29/597 [721 In Heinz Wilkc; Claus Bertram, h of 3,407,491 10/1968 Clevenger et al.. ..29/597 desheim, Germany 3,478,421 11/1969 Preece ..29/597 [73] Assignee: Robert B h GmbH Stuttgart, Germany 3,482,307 12/ 1969 Yamaguch1 ..29/597 [22] Filed: June 26, 1970 Primary ExaminerJohn F. Campbell Assistant Examiner-Carl E. Hall 1 1 pp N011 50,095 Attorney-Michael s. Striker 30 Foreign Application Priority Data [57] ABSTRACT A pair of annular blanks, one consisting of copper and one July 5, 1969 Gennany ..P 19 34 213.3 consisting of another metal, are confined in a die. A stamp is introduced into the die and the material of the blanks is cold- [52] U.S. Cl ..29/597, 29/4701, 72/258, extruded through an annular gap defined between the Stamp 310/235 310/236 and the die, to form a commutator ring an inner annular zone [51] Int. Cl ..HOlr 43/00 of which consists f the other metal whereas an outer annular Field of Search zone consists at least at one axial endface of copper. The other 72/258 metal may be aluminum and will be cold-welded or fused with the copper at the interface of the two metals. [56] References Cited 7 Claims, 5 Drawing Figures UNITED STATES PATENTS 2,953,698 9/1960 Gianotto ..29/597 X Patented May 23, 1972 v INVENTORS Heinz W/LKE Claus BERTRAM WKM their ATTORNEY BACKGROUND OF THE INVENTION The present invention relates generally to commutators, and more particularly to a novel lamella ring for such commutators and to a method of making the same.

The function and construction of a commutator are well known and require no detailed discussion. It will therefore suffice to recall briefly, by way of introduction, that in electrical apparatus the current flowing in the armature windings is supplied or removed via a commutator having a hub of insulating material which is mounted on the motor shaft. An annulus of lamellas is anchored in or to the hub and connected with the lead wires ofthe armature windings. Carbon brushes contact an axial endface of the annulus, which endface is composed of surface portions of the respective lamellas; the supply and take-off of electricity is effected via these brushes.

Because of the friction between brushes and lamellas during rotation of the commutator, there is evidently a certain amount of wear on the contacting components. To reduce this, and also to keep the electrical resistance as low as possible, the lamellas are made of copper which material has long known to be excellently suited for the purpose. However, the price of copper has steadily increased in recent years and to make the lamellas in their entirety from this material is no longer economically justifiable. Heretofore, though, no acceptable alternative has become known.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the aforementioned problem.

More particularly it is an object of the invention to provide a novel commutator which overcomes the problem in question.

It is a further object of the invention to provide a method of making such a novel commutator.

In pursuance of the above object, and others which will become apparent hereafter, one aspect of the invention resides in a method of making a commutator. This method, briefly stated, comprises the steps of making at least one blank of copper and at least one blank of another metal. These blanks are then jointly subjected to cold pressing in a manner requisite to effect their deformation to a lamella-ring configuration with simultaneous flowing of the copper to an outer annular zone, and of the other metal at least in part to an inner annular zone of the ring. At the same time, cold-welding or cold-fusing of the metals takes place at their interface. A hub of insulatingmaterial is then affixed to the ring.

In this manner, substantially less copper is required than heretofore because the copper is provided only in form of a thin layer constituting the contact face of the lamella ring. It is advantageous to use the socalled forward hollow-flowpressing method which is known per se and according to which the blanks which are of annular shape are confined in a die of requisite configuration. A stamp or ram is then introduced into the .die with which it forms a narrow annular gap. The pressure exerted by the stamp causes the material of the blanks to flow in cold state through this gap, with the materials undergoing strong stretching at their interface as they pass through the gap, resulting in cold-welding or cold-fusing of the materials at this interface.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial section showing two annular blanks for making a lamella ring according to the invention;

FIG. 2 illustrates, partly in section, a pressing apparatus accommodating the blanks of FIG. 1 and operative for converting them to a novel lamella ring;

FIG. 3 is a view analogous to FIG. 2, but showing the apparatus and the blanks subsequent to conversion of the latter;

FIG. 4 is a section taken on line IVIV of FIG. 3; and

FIG. 5 is a plan view, partly sectioned, of a commutator incorporating the lamella ring made according to FIGS. 1-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing firstly FIG. 1 it will be seen that this illustrates two annular blanks 10 and 11 which are required for making the novel lamella ring. Blank 10 is made from aluminum, blank 11 from copper, and both have identical inner and outer diameters and complementarily tapered conical endfaces 10a, 1 1a respectively.

The manner in which these blanks are produced is immaterial for the invention; they may be severed sections of tubular members, or they may be formed from sections of rod members by cold pressing and/or stamping, for instance.

A cold-press 12 is shown in FIG. 2 for converting the blanks 10 and 11 into a lamella ring. It has a two-section die 13 of which the lower section 13a has an opening 14 which is undercut at 14a to increase in diameter in downward direction. Upwardly, the opening 14 has a conically outwardly directed annular shoulder 14b and merges into a bore 15 which continues in the upper section 13b of the die 13.

A stamp or cam 16 is arranged above the die 13, mounted for movement downwardly toward and upwardly away from the die in known manner. Stamp 16 has an extension 17 which is provided on its outer circumference with regularly distributed i.e. equi-angularly spaced grooves 18 which extend in axial direction of extension 17 and are of undercut dove-tailed cross-section. The upper delimitation of extension 17 is provided by a shoulder 19, and attention is directed to the fact that the configuration of stamp 16 is such that the portion of stamp 16 which is located upwardly of shoulder 16 will fit into the bore 15 with slight clearance.

The blanks 10 and 11 (see FIG. 1) are accommodated in the bore 15 with their endfaces 10a and 11a in abutment, such that their contact face 20 conically tapers in radially inward direction, seen in direction of pressure exerted by the stamp 16. This direction is illustrated by the arrow, and it will be appreciated that as the stamp 16 moves downwardly in this direction, the extension 17 will pass through the aligned openings of the blanks l0, 11 until its leading end enters the opening 14 in the die 13. Once the shoulder 19 abuts the upwardly directed endface of the blank 10, continued movement of the stamp 16 in direction of the arrow causes the material of blanks 10 and 11 to become plastic and to flow through the narrow annular gap 21 which is defined between the extension 17 and the opening 14, as shown in FIG. 3. As this takes place, the material of the blanks is so deformed that the copper of blank 11 flows to the outer annular zones, and the aluminum of blank 10 flows to the inner annular zone of the tubular lamella ring 22 which takes shape below the annular gap 21.

As the materials pass through the gap 21 they are strongly stretched and of course subjected to pressure at their interface 20a (compare FIG. 3); this causes oxide layers at their respective surfaces to tear and allows the materials to coldweld or cold-fuse in the interface region 20a.

FIG. 4 shows clearly that as the aluminum of blank 10 flows through the annular gap 21, the dove-tail sectioned grooves 18 in extension 17 are reproduced in form of complementary axial ribs 23 at the inner periphery of lamella ring 22.

While FIG. 2 shows the apparatus ready for operation, FIG. 3 shows it at the end of its working stroke. The stamp 16 has entered into bore l5'of die 13 to such an extend that the material of blank 11 has passed entirely through gap 21; the material of blank 10 has only passed partly through the gap 21 and enough of it remains to form above the gap 21 a rein 24 which is subsequently converted into the contacts of the lamellas.

As FIGS. 3 and 4 show, the copper of blank 11 has travelled to the outer annular zone of ring 22, located below the rein 24 and which will during subsequent further processing form the contact face 28 where the commutator lamellas are engaged by the (non-illustrated) carbon brushes. The fused interface a of the two materials (of blanks 10 and 11) extends conically from the outside to the inside in direction of stamp pressure and over the length of the lamella surface 25.

FIG. 5 shows how the lamella ring 22 produced in accordance with FIGS. 1-4 is further processed for conversion to a commutator. The ring 22 is first provided with a hub 27 of insulating material, which can be done in known manner in a press die. Hub 27 has a center aperture 28 so that it can be mounted on a motor shaft. Thereupon the lamella ring 22 with its rein 24 is incised as by sawing axially to form individual commutator lamellas 29 having contacts 30, with each lamella 29 being anchored in the material of hub 27 via one of the undercut ribs 23. Finally, the contacts are provided with cuts or incisions 31 for the winding leads.

The finished commutator is shown in FIG. 5, as already pointed out. It is identified with reference numeral 26 and provided with lamellas 29 the outer layers of which in the region of the contact face are of copper while the inner zones in the region of the anchoring or securing ribs 23 and in the region of the contacts are of aluminum. The interface between the two metals is identified as 20a and this is where the metals are intimately connected by cold-welding or coldfusing. This interface 200 extends over the length of the lamella contact face 25, beginning behind the contacts 30 and continuing conically from the outer edge toward the inner edge of the lamella ring, terminating at the inner end of the respective lamella.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a commutator, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a method of making a commutaton'the steps of making at least one blank of copper and at least'one additional blank of another metal; subjecting said blanks jointly to cold pressing in a manner requisite to effect their deformation to a lamella-ring configuration with simultaneous flowing of the copper to an outer annular zone and of at least part of the other metal to an inner annular zone of said ring under concomitant cold-welding of said copper and other metal to one another at an interface thereof; affixing a hub of insulating material to the thus produced ring; and forming commutator segments from said ring.

2. In a method as defined in claim 1, both of said blanks being annular; and wherein the step of subjecting said blanks to cold-pressing comprises confining said blanks in a die, and inserting a cooperating stamp into said die to define therewith a narrow annular gap through which the material of said blanks is at least partly, forcibly extruded with concomitant strong stretching and cold-welding of the copper and other metal at their interface.

3. In a method as defined in claim 2, said blanks each having a conical endface; and wherein said endfaces abut when said blanks are in said die prior to insertion of said stamp.

4. In a method as defined in claim 2, said blanks having respective complementary endfaces each of which diverges conically in radially outward direction; and comprising the step of inserting said blanks into said die with said endfaces in mutual abutment.

5. In a method as defined in claim 2, said ram moving into said die in a predetermined direction; and wherein the material of the blank closer to said ram flows to said radially inner zone and the material of the blank farther from said ram flows to said radially outer zone.

7 6. In a method as defined in claim 2; and comprising the step of providing an outer circumferential surface of said ram with circumferentially distributed axially extending dovetailshaped grooves, so as to obtain complementary configuration on the inner circumference of said lamella ring.

7. In a method as defined in claim 2, comprising extruding the material of the blank farther from said ram completely through said annular gap, and extruding the material of the blank closer to said ram only in part through said annular gap, whereby a shoulder is formed from the material of the blank closer to said ram at one axial side of said annular gap. 

1. In a method of making a commutator, the steps of making at least one blank of copper and at least one additional blank of another metal; subjecting said blanks jointly to cold pressing in a manner requisite to effect their deformation to a lamella-ring configuration with simultaneous flowing of the copper to an outer annular zone and of at least part of the other metal to an inner annular zone of said ring under concomitant cold-welding of said copper and other metal to one another at an interface thereof; affixing a hub of insulating material to the thus produced ring; and forming commutator segments from said ring.
 2. In a method as defined in claim 1, both of said blanks being annular; and wherein the step of subjecting said blanks to cold-pressing comprises confining said blanks in a die, and inserting a cooperating stamp into said die to define therewith a narrow annular gap through which the material of said blanks is at least partly, forcibly extruded with concomitant strong stretching and cold-welding of the copper and other metal at their interface.
 3. In a method as defined in claim 2, said blanks each having a conical endface; and wherein said endfaces abut when said blanks are in said die prior to insertion of said stamp.
 4. In a method as defined in claim 2, said blanks having respective complementary endfaces each of which diverges conically in radially outward direction; and comprising the step of inserting said blanks into said die with said endfaces in mutual abutment.
 5. In a method as defined in claim 2, said ram moving into said die in a predetermined direction; and wherein the material of the blank closer to said ram flows to said radially inner zone and the material of the blank farther from said ram flows to said radially outer zone.
 6. In a method as defined in claim 2; and comprising the step of providing an outer circumferential surface of said ram with circumferentially distributed axially extending dovetail-shaped grooves, so as to obtain complementary configuration on the inner circumference of said lamella ring.
 7. In a method as defined in claim 2, comprising extruding the material of the blank farther from said ram completely through said annular gap, and extruding the material of the blank closer to said ram only in part through said annular gap, whereby a shoulder is formed from the material of the blank closer to said ram at one axial side of said annular gap. 